The invention relates to a compound turbo-drive for an exhaust-gas turbocharger and re-expansion turbine of an internal-combustion engine. The re-expansion turbine is connected to drive engine accessories through a reduction gear. The compound turbo-drive is located laterally of the cylinders in the region of the output end of the internal-combustion engine.
A compound turbo-drive of this general type is known from German patent specification 962,764. Here an exhaust-gas and re-expansion turbine are designed as axial flow turbines and are located in succession, adjacent and laterally of the engine cylinders in the longitudinal direction of the engine.
This arrangement requires a considerable space next to the internal-combustion engine. Moreover, because of this extended design, the possibility for mounting auxiliary units is restricted and it may be necessary to shift the location of these units.
An object of the invention is to develop a known compound turbo-drive it that it can be arranged in a space-saving way on internal-combustion engines with two cylinder banks arranged in V-form.
According to the invention, this object is achieved by an internal-combustion engine with two cylinder banks arranged in V-form and with a separate exhaust-gas turbocharger for each cylinder bank. The re-expansion turbine is designed with a double-flow turbine housing, located between the two exhaust-gas turbochargers, and is separately connected to the two exhaust-gas turbochargers by two respective inlet channels integrated in the turbine housing.
The invention ensures that the re-expansion turbine can be arranged between the two exhaust-gas turbochargers. This, in conjunction with the two exhaust-gas turbochargers, results in a compound turbo-drive arrangement which is located between the two cylinder banks of the internal-combustion engine and therefore is substantially symmetrically in relation to the longitudinal axis of the engine. A space-saving arrangement is obtained thereby, since the re-expansion turbine inserted between the exhaust-gas turbochargers does not take up any additional constructional space. Another advantage is obtained because the symmetrical arrangement of the compound turbo-drive allows the exhaust-gas lines leading from the two cylinder banks to the exhaust-gas turbochargers to be made of approximately equal length. This allows for a uniform loading for the exhaust-gas turbines.
By having the re-expansion turbine inlet channels guided away from the turbine housing in opposite directions and by having the exhaust-gas turbochargers flanged directly to these inlet channels through outlet flanges facing the re-expansion turbine housing, an especially compact design of the compound turbo-drive is obtained. Here the exhaust gases from the two exhaust-gas turbines of the exhaust-gas turbochargers are diverted into the re-expansion turbine along the shortest possible path and therefore without further energy losses. By having the exhaust-gas turbochargers and the re-expansion turbine form a single constructional unit which is supported on part of the crankcase through a flange to the gear casing of the reduction gear, it is possible to combine the constructional elements of the compound turbo-drive independently of the internal-combustion engine. During final assembly of the internal-combustion engine, this unit merely has to be mounted on at the intended location of the engine housing. This ensures an efficient assembly of the compound turbo-drive.
To ensure that the effective power obtained at the service turbine is transmitted to the crankshaft with the highest possible efficiency, it is advantageous if the gear casing of the reduction gear is supported directly on the crankcase, or on a control casing mounted on the crankcase. Advantageously, the necessary internal-combustion engine drive mechanism for driving the camshaft (or other auxiliary drives) can also be included in the transmission of the effective power train from the re-expansion turbine. This results in the reduction gearing being produced with a smaller number of gearwheel mechanisms. It is especially favorable if the reduction gear is meshed with the driving gearwheel of the camshaft.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.